As shown in FIG. 1, a rowing exercise machine 1 of the prior art is composed of a base 2, two pedals 3 fastened pivotally with one end of the base 2, two oil-pressure rods 4 fastened pivotally at one end thereof with the base 2, two slide rods 5 fastened pivotally with the oil-pressure rods 4 such that the slide rods 5 are slidable on the base 2, and a seat 6 fastened with another end of the base 2 such that the seat 6 is opposite to the pedals 3. The rowing exercise is brought about by a person who is seated on the seat 6, with his or her hands holding the slide rods 4 and with his or her feet pressing against the pedals 3. In other words, the rowing exercise machine 1 of the prior art is intended for use by a person to develop the muscles of arms and legs of the person.
Such a prior art rowing exercise machine as described above is defective in design in that the damping effect of the oil-pressure rods 4 can not be adjusted to suit the physical conditions of an exerciser. As a result, the prior art rowing exercise machine is rather limited in use.